Abstract. Modern programming languages have little or no support for querying objects and collections. Programmers are forced to hand code such queries using nested loops, which is both cumbersome and inefficient. We demonstrate that first-class queries over objects and collections improve program readability, provide good performance and are applicable to a large number of common programming problems. We have developed a prototype extension to Java which tracks all objects in a program using AspectJ and allows first-class queries over them in the program. Our experimental findings indicate that such queries can be significantly faster than common programming idioms and within reach of hand optimised queries. 1

We present DITTO, an automatic incrementalizer for dynamic, sideeffect-free data structure invariant checks. Incrementalization speeds up the execution of a check by reusing its previous executions, checking the invariant anew only on the changed parts of the data structure. DITTO exploits properties specific to the domain of invariant checks to automate and simplify the process without restricting what mutations the program can perform. Our incrementalizer works for modern imperative languages such as Java and C#. It can incrementalize, for example, verification of red-black tree properties and the consistency of the hash code in a hash table bucket. Our source-tosource implementation for Java is automatic, portable, and efficient. DITTO provides speedups on data structures with as few as 100 elements; on larger data structures, its speedups are characteristic of non-automatic incrementalizers: roughly 5-fold at 5,000 elements, and growing linearly with data structure size.

This paper describes a transformational method applied to the core component of role-based access control (RBAC), to derive efficient implementations from a specification based on the ANSI standard for RBAC. The method is based on the idea of incrementally maintaining the result of expensive set operations, where a new method is described and used for systematically deriving incrementalization rules. We calculate precise complexities for three variants of efficient implementations as well as for a straightforward implementation based on the specification. We describe successful prototypes and experiments for the efficient implementations and for automatically generating efficient implementations from straightforward implementations.

For the last 15 years, implementors of multiple view programming environments have sought a single code model that would form a suitable basis for all of the program analyses and tools that might be applied to the code. They have been unsuccessful. The consequences are a tendency to build monolithic, single-purpose tools, each of which implements its own specialized analyses and optimized representation. This restricts the availability of the analyses, and also limits the reusability of the representation by other tools. Unintegrated tools also produce inconsistent views, which reduce the value of multiple views. This paper describes an architecture that allows a single, minimal representation of program code to be extended as required to support new tools and program analyses, while still maintaining a simple and uniform interface to program properties. We present architectural patterns that address efficiency, correctness and the integration of multiple analyses and tools in a modular fashion.

Abstract. Many contemporary object-oriented programming languages support first-class queries or comprehensions. These language extensions make it easier for programmers to write queries, but are generally implemented no more efficiently than the code using collections, iterators, and loops that they replace. Crucially, whenever a query is re-executed, it is typically recomputed from scratch. We describe a general approach to optimising queries over mutable objects: query results are cached, and those caches are incrementally maintained whenever the collections and objects underlying those queries are updated. We hope that the performance benefits of our optimisations may encourage more general adoption of first-class queries by object-oriented programmers. 1

This paper describes a language and framework that allow coordinated transformations driven by invariants to be specified declaratively, as invariant rules, and applied automatically. The framework supports incremental maintenance of invariants for program design and optimization, as well as general transformations for instrumentation, refactoring, and other purposes. This paper also describes our implementations for transforming Python and C programs and experiments with successful applications of the systems in generating efficient implementations from clear and modular specifications, in instrumenting programs for runtime verification, profiling, and debugging, and in code refactoring.

This paper describes a framework that supports powerful queries in debugging tools, and describes in particular the transformations, alias analysis, and type analysis used to make the queries efficient. The framework allows queries over the states of all objects at any point in the execution as well as over the history of states. The transformations are based on incrementally maintaining the results of expensive queries studied in previous work. The alias analysis extends the flow-sensitive intraprocedural analysis to an efficient flow-sensitive interprocedural analysis for an objectoriented language with also a form of context sensitivity. We also show the power of the framework and the effectiveness of the analyses through case studies and experiments with XML DOM tree transformations, an FTP client, and others. We were able to easily determine the sources of all injected bugs, and we also found an actual bug in the case study on the FTP client. 1.

This paper describes a corrected and simplified specification of role-based access control (RBAC) based on the specification in the ANSI standard for RBAC. We give a complete specification of core RBAC, explaining the methodology we used in developing it; we then give a complete specification of hierarchical RBAC, with an additional option for managing the relationship on roles; and we also describe a specification of constrained RBAC, making extension relationships among RBAC components clear. We compare our specification with the standard and point out errors and unnecessary complications we found. We also describe the principles for developing clear and simpler specifications, and summarize our method and results for generating efficient implementations. 1

Dynamic languages such as Python allow programs to be written more easily using high-level constructs such as comprehensions for queries and using generic code. Efficient execution of programs then requires powerful optimizations— incrementalization of expensive queries and specialization of generic code. Effective incrementalization and specialization of dynamic languages require precise and scalable alias analysis. This paper describes the development and experimental evaluation of a may-alias analysis for a full dynamic objectoriented language, for program optimization by incrementalization and specialization. The analysis is flow-sensitive; we show that this is necessary for effective optimization of dynamic languages. It uses precise type analysis and a powerful form of context sensitivity, called trace sensitivity, to further improve analysis precision. It uses a compressed representation to significantly reduce the memory used by flowsensitive analyses. We evaluate the effectiveness of this analysis and 17 variants of it for incrementalization and specialization of Python programs, and we evaluate the precision, memory usage, and running time of these analyses on programs of diverse sizes. The results show that our analysis has acceptable precision and efficiency and represents the best trade-off between them compared to the variants.

This paper describes a very high-level language for clear description of distributed algorithms and optimizations necessary for generating efficient implementations. The language supports high-level control flows where complex synchronization conditions can be expressed using high-level queries, especially logic quantifications, over message history sequences. Unfortunately, the programs would be extremely inefficient, including consuming unbounded memory, if executed straightforwardly. We present new optimizations that automatically transform complex synchronization conditions into incremental updates of necessary auxiliary values as messages are sent and received. The core of the optimizations is the first general method for efficient implementation of logic quantifications. We have developed an operational semantics of the language, implemented a prototype of the compiler and the optimizations, and successfully used the language and implementation on a variety of important distributed algorithms.